Study supports widespread use of better masks to combat COVID-19 indoor
PESHAWAR: Better face masks and good ventilation greatly reduce the risk of spreading COVID-19 indoors, a study found.
University of Waterloo engineering researchers, using a mannequin to simulate a seated person breathing in a large room, found a significant buildup over time of aerosol droplets despite the use of common cloth and blue surgical masks.
Those tiny, exhaled droplets remain suspended and travel through the air, potentially exposing anyone else in the room to the virus.
“There is no question it is beneficial to wear any face covering, both for protection in close proximity and at a distance in a room,” study leader Serhiy Yarusevych, a professor of mechanical and mechatronics engineering, said. “However, there is a very serious difference in the effectiveness of different masks when it comes to controlling aerosols.”
Previous research found that aerosols dispersed by infected people are a source of transmission of the virus that causes COVID-19, even outside the two metres recommended by public health officials, Science Daily reported.
Commonly used masks only filter about 10 per cent of exhaled aerosol droplets — primarily due to problems with fit. The remaining aerosols escape into the air, mostly out the top of the mask where it fits over the nose.
Those aerosols can accumulate indoors and spread the COVID-19 virus when inhaled by other people.
Higher-quality, more expensive N95 and KN95 masks filtered more than 50 per cent of the exhaled aerosols.
Yarusevych said the much greater effectiveness of N95 and KN95 masks, compared to cloth and surgical masks, makes a good case for those being worn indoors as much as possible.
“A lot of this may seem like common sense,” he said. “There is a reason, for instance, that medical practitioners wear N95 masks — they work much better. The novelty here is that we have provided solid numbers and rigorous analysis to support that assumption.”
The researchers also tested the impact of ventilation systems on the accumulation of aerosols. Even modest ventilation rates were found to be as effective as the best masks in reducing the risk of transmission.
The safest approach would be a combination of high-quality masks and proper ventilation to reduce the risk of aerosols accumulating, found the study appearing in the journal Physics of Fluids. - APP